HOP 0096

abstract of observational proposal

Observations of active regions with EIS in the first two years of Hinode operations have revealed that virtually all active regions show significant line broadening and apparent (see below) outflows in areas that are weak in intensity. An example of this effect is shown in Doschek et al. (2007). In addition, observations with XRT have demonstrated continuous apparent outflow in open or extended loop structures (Sakao et al. 2007, Korreck et al. in prep). Doschek et al. (2008) furthers this evidence for outflows and connects these regions as possible sources of heliospheric magnetic fields. These outflows are an exciting new discovery from Hinode, and are a potential source of the slow solar wind.

The Sakao et al. observation demonstrated the value of continuous, uninterrupted observations of the footpoints region as they observed active region AR 10942 for three complete days. Unfortunately the EIS observations at this time were not homogeneous, consisting of several different studies pointed at different locations in the active region. By systematically using the same EIS sequence at the same location for 6 continuous days we can make a definitive statement about whether the EIS outflows are related to the XRT outflows, and we will investigate how the flows vary with longitude. In particular, by observing the region towards the west limb, we hope to associate the outflows with in situ measurements from the ACE spacecraft that would make a clear association of the AR outflows with the slow solar wind.

request to SOT

SOT data are vital for identifying the photospheric and chromospheric roots of the loop footpoints, and measuring the vector magnetic field. A Spectro-Polarimeter (SP) observations are requested over a spatial region of 180”x164” once an hour each day, interspersed with BFI images in G-band, Ca II and H-alpha (focus optimised for Ca II).

SOT comments:
I had an action item to look at Kelly Korreck's HOP 96 proposal, which proposed dropping the SOT telemetry allocation to 15%. Here is the response that I sent to her (unfortunately, only yesterday).

First, the easy questions about the requested SOT observations. It is a reasonable program to run for this purpose. Taking your request literally, the SP fast maps would use about 2,100 Mbits/day (340 Mbits each) and the filter images about 800 Mbits/day (assuming one set every 10 minutes). Each SP map takes about 35 minutes to make. This total telemetry, 2900 Mbits, is a little more than our normal daily allocation nowdays (70% of the total).

A reasonable fallback position might be 2 SP maps (at the start and end of the EIS observations) instead of 6 and one-quarter of the filter image total through a combination of higher than usual compression and lower cadence. This could get the SOT total down to between 20 and 25% of the typical total daily allocation.

I'm not opposed in principle to a program like this with low SOT telemetry, if the monthly meeting agrees that it is a good science priority and the telemetry is really needed by the other instruments. I would not agree to run it on the first (or 2nd or 3rd) good AR that comes along after the present drought, because SOT (and Hinode) have a number of other high priority programs which have been waiting for a good AR. But I would agree for the Nth, where we can discuss the value of N.

I will leave it to the EIS folks to estimate how much of the telemetry they really need for your program.

I also have some concern about all 3 instruments burning our entire telemetry allocations in 4 or 6 hours of the day, for 6 days in a row; I think we should hold some in reserve for capturing the evolution of the region in the remaining time and perhaps for a flare response.

Tom Berger pointed out the following:
"Is another concern about filling the DR in 4--6 hours per day for 6 days in a row is that it may require special pass management to avoid having many "blank" downloads later in the timeline?"

I'm not sure if this will cause a problem or not in pass management. My point was that the instruments should hold back a little telemetry so we are not idle for the remaining 18-20 hours per day.

Kelly replied "I am going to see if I can't rework it in a way that science is still done but that doesn't pile up the data in 6 hours. "

Best regards,

Ted

request to EIS

EIS will run the study PRY_footpoints_HI2 which is identical to the well-used PRY_footpoints_v2 study except that the raster covers 512” in Y instead of the current 240”. This accounts for the increased share of the data recorder for EIS. The increased field of view in Y allows EIS to access quiet Sun areas that can be used as a reference to fix the wavelength scale for velocity determinations.
Notes for EIS CO: The block should begin with a context study PRY_slot_context_v2 (duration 3 minutes), and then PRY_footpoints_HI2 should be repeated to fill the block. For the following blocks, make sure to use the same mirror position (MIP) as the previous block to ensure that PRY_footpoints_HI2 is pointed in exactly the same place each time. Check with David Williams or David Brooks if you are not sure how to do this.

remarks

Assuming a smaller fixed data rate after January 2008, an extension of solar-Y coverage to include quiet Sun regions means losing spectral information yet it is only with a wide range of emission lines that we can probe the temperature, density, and velocity structure of the outflow regions. Our solution for this HOP is to allocate a greater share of the data recorder (DR) to EIS, thus allowing greater spatial coverage and retaining wide spectral coverage. The normal EIS DR allocation is 15%. For this specific study we request 50% (see below for justification). XRT requests 35%, and SOT will be reduced to 15%. In order to investigate the time variability of the outflows, it is essential to obtain a long, continuous set of observations. We thus make the following special observing requests:

・for each of the six days, a single 6 hour observing run is made;
・to minimize disruption of the sequence, we request only 2 XRT

synoptics each day;
・the observation begins at the start of a single upload plan on Day 1, and ends at the end of the Day 6 upload plan (so that the modified DR allocations only affect six Hinode planning days)
・if the instruments have particular engineering or calibration sequences that must be run during the 6 day period, then we request that the instrument teams schedule them for the same time slot to minimize any disruption to the coordinated data-set

Target/Pointing
A well-developed active region close to disk center. The target will be the base of large loop structures found near the edge of the active region (see Figure 1 above). The SOT pointing should be at the footpoints of the loops. E.g., in Figure 1 the centre of the SOT field of view would be approximately (-360,-50). Duration The study should be run for six days for a 6 hour period each day.